Cutinases (EC 3.1.1.74) are hydrolytic enzymes, i.e. hydrolases, that degrade cutin, a component of the plant cuticle that, in addition to waxes, constitute the outermost continuous membrane or “skin” of the primary parts of higher plants. Cutin is a polyester, largely composed of saturated C16 (palmitic) acids and unsaturated C18 fatty acids cross-linked by ester bonds; the actual composition of which depends on the plant species. The cuticle primarily protects plants from water loss or other environmental stresses, thereby acting as a formidable barrier.
Cutinases have been found predominantly in phytopathogenic fungi as secreted enzymes to facilitate their entry into the host plant. The prototypical cutinase is the FsCUT derived from Fusarium solani f. sp. pisi (aka Nectria haematococca) that infects peas. This enzyme plays a role in plant pathogenesis as a virulence factor, but not exclusively since hydrophobic surface binding proteins, called hydrophobins, are also involved. FsCUT is a 230-amino acid enzyme synthesized with a 31 amino-acid signal peptide, with the mature, secreted portion having a molecular mass of 21,600 Da (Soliday et al., 1984). Its structure belongs to the α/β class of hydrolases containing the classical Ser-His-Asp triad (S120, H188 and D175) for catalysis (Martinez et al., 1992).
Owing to the hydrolytic, esterification or transesterification activities, both naturally-occurring or genetically-modified cutinases of Fusarium and other organisms, have been produced and applied to varying extent in industries such as food, laundry and detergent, textiles, recycling, and polymer manufacturing.